Various calixarene-type compounds and self-assembled and spherical hexamers of calixarene derivatives have been proposed for various applications. For example, MacGillivray and Atwood in a paper entitled “A Chiral Spherical Molecular Assembly Held Together by 60 Hydrogen Bonds,” Nature, Vol. 389, pp. 469-472, October 1997, disclose a self-assembly mechanism for methylcalix[4]resorcinarenes self-assembled as a spherical hexamer along with adventitious water molecules. MacGillivray et al disclose the use of methylene-bridged resorcinarenes to form hexameric superstructures. MacGillivray makes reference to exploring various applications including a chiral catalyst for chemical transformations, a micro-vesicle for drug delivery, and an intermediate for separation problems.
Subsequent to the MacGillivray/Atwood paper, Gerkensmeier et al in a paper entitled “Self-Assembly of 2,8,14,20-Tetraisobutyl-5,11,17,23-tetrahydroxyresorc[4]arene,” European Journal of Organic Chemistry, 1999, pp. 2257-2262, discuss self-assembling systems based upon hydroxyresorcinarenes generated by the acid catalyzed condensation of 2-hydroxyresorcinol (pyrogallol) with aldehydes in polar media. Here, the self-assembly products were characterized as two-dimensional polymeric structures held together by hydrogen bonds. The Gerkensmeier et al paper does, however, report on the preparation of a spherical hexamer having an enclosed interior space populated by ten solvent molecules. However, attempts to replicate this hexamer structure were unsuccessful, and the structure was characterized by Gerkensmeier et al as being very fragile due to its being stabilized by weak hydrogen bonds.
The self-assembled host structures arrived-at through procedures, such as described in MacGillivray/Atwood and Gerkensmeier et al papers, are in the form of molecular structures which are maintained through chemical bonding such as covalent bonding or hydrogen bonding. Thus, as described in the MacGillivray/Atwood paper, the calixarene-based hexamers are sustained through intermolecular bonding formed predominantly through hydrogen bonds involving the adventitious water molecules.